1. Field of the Invention
The present invention relates to a syringe barrel suitable for injection at high injection pressure using a driving mechanism such as an automatic injector and the like; a cylinder holder used for a syringe driving mechanism such as an automatic injecting apparatus and the like; syringe piston; and piston holder.
2. Description of the Related Art
Syringes are used for injection of liquid in various fields typically including a medical field. Injection of a chemical solution having high viscosity such as a contrast agent for X ray CT imaging and a contrast agent for MRI (magnetic resonance imaging apparatus) requires high pressure, causes difficulty in manual handling, and makes intense jobs. Therefore, it is general to effect injection using a mechanical syringe driving mechanism such as an automatic injection apparatus and the like. FIG. 11 shows a syringe 20 to be mounted on such an automatic injecting apparatus 10. The automatic injecting apparatus 10 comprises a cylinder holder 11, a piston holder 12, and a motor inside (now shown), and the cylinder holder 11 fixes a syringe barrel 21 by holding a flange 22 and the piston holder 12 holds a piston flange 24. A piston 23 can be moved relative to the syringe barrel 21 by progressing or regressing the piston holder 12 by a motor, to effect injection (discharge of liquid from the syringe) or suction of liquid. FIG. 12 shows the syringe 20 mounted on the automatic injecting apparatus 10.
Further, as shown in FIG. 13, when a syringe of smaller size is mounted on this automatic injecting apparatus, the syringe barrel 21 is mounted on a dismountable adaptor 13 (functions as a cylinder holder for the syringe) which is further mounted on the automatic injecting apparatus 10. FIG. 14 shows the syringe 20 mounted on the automatic injecting apparatus 10.
FIG. 16 provides detailed drawings of the adaptor 13 ((a) is a plan view, and (b) is a rear side view)). The syringe barrel 21 can be held by fitting the flange 22 of the syringe barrel 21 into a flange insertion groove 14 of the adaptor 13. For the mounting, as shown in FIG. 15(a), the flange 22 is fitted into the flange groove 14 while directing a flange cut portion 25 vertically. Then, the flange is rotated by 90.degree. to be fixed so that it is not disconnected. FIG. 15(b) is a view showing the rotating process, and FIG. (c) is a view showing the use position.
In this constitution, the flange thickness and the flange insertion groove width are so designed to give slight clearance between the flange and flange groove for enabling smooth mounting of the syringe barrel. The reason for this design is also that if the clearance is designed to zero completely, mounting may be sometimes impossible due to certain extent production error to be taken into consideration because the syringe barrel and the cylinder holder (including the adaptor) are usually formed of different materials. Consequently, slight backlash and play in mounted condition is inevitable. However, if there is an error in the mounting procedure, the syringe may sometimes be raised from the right position. If injection of a contrast agent and chemical solution is conducted when fitting in such slight clearance is displaced, the piston shall be pushed under condition in which the flange 22 is inclined relative to the flange insertion groove 14, as shown schematically in FIG. 17, and the total pressure is concentrated only on a part of the flange, and resultantly, in the worst case, the flange may be occasionally broken particularly from the base part.
The cut part of the flange is necessary also for prevention of syringe from rolling down when it is left on a plat surface such as on a table, in addition for such position determination.
Further, the syringe mentioned herein is the enlarged version (100 mL, 200 mL) of a syringe having a generally prevailing form composed of a syringe barrel and a piston. While a generally-used 50 to 60 mL syringe has a pressure resistance of about 3 kg/cm.sup.2, the syringe herein shown has an increased pressure resistance of about 20 kg/cm.sup.2 to be used for injecting a contrast agent.
On the other hand, there is also a syringe for a contrast agent of no piston type. In this type of syringe, a female screw provided on a member fixing a packing and a male screw on the tip of an axis on the injection apparatus side are connected and the axis is driven back and forth, to suck and inject a contrast agent. However, since such a syringe of no piston type is dedicated to an injector, an automatic injecting apparatus should necessarily used also in sucking a chemical solution. Therefore, during diagnosis, since the automatic injecting apparatus is occupied, sucking of a chemical solution is impossible.
However, a syringe of generally spread type as shown in FIG. 11 and the like has a merit that a chemical solution is filled in the syringe and is prepared previously as a chemical solution for the next inspection, even in diagnosis, since suction of a chemical solution is possible even manually and consequently an automatic injecting apparatus is not necessarily occupied. Further, as shown in FIGS. 11 and 13, there are also a merit that even syringes of different sizes can adopt the same injecting apparatus by using an adaptor, a merit that mounting to an apparatus is easy, and the like.
As described above, there have been made various improvements in syringes for injecting a chemical solution such as a contrast agent and the like, however, when a chemical solution having high viscosity such as a contrast agent is injected, strong force is applied to a flange, consequently, the syringe may occasionally be broken if there are a small number of flange surfaces receiving pressure. If the flange is not rotated to given position and if injection is conducted, for example, in halfway condition as shown in FIG. 15 (b), crisis of breakage increases due to small area receiving pressure. Further, in an apparatus for injection using a relatively large syringe having a size of about 200 mL, there has been recently contrived a mechanism for clamping in which a cylinder holder portion is mobilized and mounting of a flange can be effected simply and securely. FIG. 18 is an enlarged view of a cylinder holder portion of such an automatic injecting apparatus 110. This cylinder holder has two clamps 116, and before mounting of a 30 syringe, the upper part of two clamps are open as shown in FIG. 18. Then, in FIG. 19(a) (upper left view in FIG. 19), the syringe is fitted in two clamps 116 in open state while directing the flange cut surface vertically. With progress of fitting, two clamps 116 are pushed by the flange 122 and rotated around the fulcrum 117, leading to closed condition. By rotating the flange by 90.degree., the syringe is fixed while the flange cut surfaces 125 being situated at upper and lower positions as shown in FIG. 19(b) (upper right view in FIG. 19). FIG. 19(c) is a plan view of the fixed condition watched from the upper side (clamp part is drawn in sectional view).
However, even if such a clamp mechanism is used, when a syringe is fixed at a halfway position in a process from FIG. (a) to FIG. (b), the pressure-receiving area of the flange decreases in injection and crisis of syringe breakage increases like the above-mentioned case.